RAD50 and microcephaly: Heterozygous and homozygous mutations in the RAD50 gene have been reported in two patients with a NBS-like disorder (NBSLD [OMIM 613078]) phenotype, who exhibit microcephaly, growth retardation, and reduced ATM kinase signaling [8,9]; however, it is difficult to evaluate the pathophysiology of RAD50 mutations in humans because these mutations are rare.